Study variety in a partner (7)
I believe the answer is:
consort
'partner' is the definition.
(I know that consort is a type of partner)
'study variety' is the wordplay.
'study' becomes 'con' (con can mean to study).
'variety' becomes 'sort' (synonyms).
'con'+'sort'='CONSORT'
'in a' acts as a link.
(Other definitions for consort that I've seen before include "wife, perhaps" , "Spouse, partner" , "Monarch's husband" , "Husband or wife of a monarch" , "Group playing music" .)